For IDPs, a dynamic ensemble of conformations characterizes its `structure' [1]}. But, a fundamental yet unresolved question is how much IDPs can be treated as conventional polymers, or should we consider intramolecular structural heterogeneity (ISH) derived from amino acid sequence to describe IDPs better? Some IDPs have minimal sequence heterogeneity (e.g., PAS repeats [2]}, [3]}, GRGDSPYS repeats [4]}, SR and RRRRR repeats [5]}, FG repeats [6]}), and thus expected to behave as conventional long homopolymers. However, other more heterogeneous IDPs did show discrepancies to these polymeric models [7]}, [8]}. Therefore, evaluating ISH may highlight fundamental properties and their relation to the IDPs' sequence, leading to unravel their function.
